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General Certificate of Education
June 2006
Advanced Level Examination
BIOLOGY (SPECIFICATION B)
BYB678/B
Unit 6 Section B Applying Biological Principles
Unit 7 Section B Applying Biological Principles
Unit 8 Section B Applying Biological Principles
Friday 23 June 2006
1.30 pm to 3.45 pm
For this paper you must have:
● Section A
● a ruler with millimetre measurements
You may use a calculator
For Examiner’s Use
Number
Mark
Number
Mark
1
Time allowed: The total time for Section A and Section B of this
paper is 2 hours 15 minutes
2
Instructions
● Use blue or black ink or ball-point pen.
● Fill in the boxes at the top of this page.
● Answer all questions.
● Answer the questions in Section B in the spaces provided.
● Section A and Section B will be marked by different examiners.
You must ensure that any supplementary sheets are fastened to the
appropriate question paper answer book.
● Do all rough work in this book. Cross through any work you do not
want marked.
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3
Total (Column 1) →
Total (Column 2) →
TOTAL
Examiner’s Initials
Information
● The maximum mark for Section B is 50.
● The marks for questions are shown in brackets.
● You are reminded that all questions in this Section B are synoptic
(indicated by the letter S). You must use your knowledge of different
parts of the specification when answering this section.
● You are advised to spend 1 hour 15 minutes on Section B.
● Use accurate scientific terminology in all your answers.
● You are reminded of the need for good English and clear presentation
in your answers. Question 4 should be answered in continuous prose.
Quality of Written Communication will be assessed in your answer.
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SECTION B
Answer all questions in the spaces provided.
S 1 A large number of roots from many genetically identical bean plants were cut into short
pieces. The pieces were sorted into groups, depending upon their distance from the root tip.
Some pieces from each group were used to find the mean dry mass of their cells. Thin
sections cut from other pieces were examined with a light microscope to find the proportion
of dividing cells and the mean volume of the cells.
The graph shows the results. The diagrams below the graph show the appearance of cells in
light microscope sections at different distances from the root tip.
Mean cell volume
Proportion of
dividing cells
Increase
Mean dry mass
0
Cell wall
Nucleus
Cytoplasm
1
2
3
4
5
Distance from root tip / mm
Vacuole
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(a) Suggest two variables, other than genotype, which need to be controlled to ensure
similar root growth in different plants. In each case give the reason for your answer.
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(2 marks)
(b) Describe how you would find the dry mass of a sample of pieces of root.
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(2 marks)
(c) Suggest how the proportion of dividing cells in a thin section could be determined.
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(2 marks)
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(d) Explain the change in the proportion of dividing cells with increasing distance from
the root tip.
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(2 marks)
(e) Using the graph and diagrams, suggest how a root tip gets longer.
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(3 marks)
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S 2 Figure 1 shows the life cycle of a species of insect. Adults lay eggs which hatch into larvae.
Larvae feed and grow and eventually turn into pupae. During the pupal stage, no feeding
takes place and the adult body is formed. The adults and larvae feed on plants.
Figure 1
Diapause
First adult
generation
emerges in
spring
Egg
Pupa
Larva
Larva
Egg
Second adult
generation
emerges in summer
Pupa
(a) Pupae that develop in late summer enter diapause, a state in which the rate of
metabolism is very greatly reduced. Adults do not emerge from these pupae until the
following spring. This is an adaptation to changes in food availability and abiotic
conditions. Explain how a slower metabolic rate is of benefit to the insect.
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(3 marks)
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(b) The factors which bring about diapause were investigated. Three groups of larvae,
A, B and C, were exposed to different patterns of light and dark periods during each
24 hours for several days. It was noted whether or not diapause developed in the
pupae that formed later. Figure 2 shows the results.
Figure 2
0h
0h
Light period
Diapause
in pupae
18 h
Dark period
No
diapause
18 h
6h
0h
12 h
6h
12 h
Group B
Group A
18 h
No
diapause
6h
12 h
Group C
Is it the length of the light period or the length of the dark period that affects whether
diapause develops? Give evidence from Figure 2 to support your answer.
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(3 marks)
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S 3 Clover plants have leaves all through the year. Some clover plants have leaves that produce
poisonous hydrogen cyanide gas when damaged. These cyanogenic plants are less likely to
be eaten by snails. However, the leaves of these plants can be damaged by frost, resulting in
the production of enough hydrogen cyanide to kill the plants. Acyanogenic plants do not
produce hydrogen cyanide. This characteristic is genetically controlled.
The map shows the proportions of the two types of plant in populations of clover from
different areas in Europe. It also shows isotherms, lines joining places with the same mean
January temperature.
Key
Black area represents
proportion of plants
able to produce
cyanide (cyanogenic)
White area represents
proportion of plants
not able to produce
cyanide (acyanogenic)
–9.0° C
4.4° C
–4.4° C
0° C
2.0° C
8.0° C
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(a) Explain how different proportions of cyanogenic plants may have evolved in
populations in different parts of Europe.
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(4 marks)
(b) Differences in cyanide production may affect the total number of clover plants growing
in different areas. Describe how you would use quadrats in an investigation to
determine whether or not there is a difference in the number of clover plants in two
large areas of equal size.
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(4 marks)
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S 4 Write an essay on one of the topics below.
EITHER
(a) The transfer of substances containing carbon between organisms
and between organisms and the environment
(25 marks)
OR
(b) Cells are easy to distinguish by their shape.
How are the shapes of cells related to their function?
(25 marks)
In the answer to this question you should select and use relevant principles and concepts from
different parts of the specification.
Your essay will be marked not only for its scientific accuracy, but also for the selection of
relevant material.
Write your essay in continuous prose.
The maximum number of marks that can be awarded is:
Scientific content
Breadth of knowledge
Relevance
Quality of Written Communication
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END OF QUESTIONS
For Examiner’s use only
Mark
Comment
S
B
R
Q
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